HDACs are a group of enzymes for regulating a series of biological effects including chromatin recombination, transcription activation or inhibition, cell cycle, cell differentiation, cell apoptosis and so on by inducing histone deacetylation at the level of cell chromatin, and are in particular related to gene transcription expression regulation after cell activation. HDAC inhibitors (HDACIs) are compounds for inhibiting the activity of the HDACs.
Histone acetylation plays a very important role in DNA transcription, replication and repair processes of the chromosomes. The HDAC inhibitors have been used as mood stabilizers and antiepileptic drugs in the past. In recent years, people begin to pay attention to the targeted therapy of the HDAC inhibitors on neurodegenerative diseases. Histone acetylation and deacetylation of chromatin are one of the key links for regulating the gene expression, and abnormal gene expression is the molecular biology basis of tumors and some genetic and metabolic diseases. The histone acetylation degree is coordinated and controlled by histone acetylase (HAT) and HDAC. Experiments prove that the HDAC inhibitors will improve the level of the chromatin histone acetylation, resulting in specific expression of gene activation, correspondingly causing terminal differentiation of cells or apoptosis of cancer cells. Therefore, HDAC has become one of the hottest targets at present in the field of research and development of tumor chemotherapeutics.
At present, it has been known that HDACs have 18 different subtypes and include four categories according to the germ line: I (HDAC1, 2, 3, 8), II (HDAC4, 5, 6, 7, 9, 10), III (SIRT1-SIRT7) and IV (HDAC11), wherein I, II and IV are classical families and are Zn2+-dependent HDACs. Most of HDAC inhibitors in the current clinical research can inhibit several subtypes of HDACs, and these subtypes often belong to the Zn2+-dependent HDAC family.
The HDAC inhibitors can inhibit the activity of HDACs in cells, so that the degree of the histone acetylation in the cells increases and the expression of genes (such as p21 and p53) improves, so the tumor cells are inhibited to proliferate and induced for differentiation and apoptosis. The HDAC inhibitors usually comprise three parts of a zinc ion binding region, a linkage region and a surface recognition region. The direct action of the inhibitor with zinc ions is indispensable to the inhibition of the activity. The HDAC inhibitors mainly include the following four categories: (1) short-chain fatty acids, such as butyric acid, phenylbutyric acid and salt compounds thereof; (2) compounds of hydroximic acids, such as suberoylanilide hydroxamic acid (SAHA) and trichostatin A (TSA), which are the most widely studied; (3) compounds of cyclic tetrapeptides, compounds of cyclopeptides are inhibitors with the most complex structure, the amino acid large cyclo in the molecule of inhibitors of cyclopeptides is used as the hydrophobic surface recognition region, the alkyl chain is used as the linkage region, the alkyl chain end is linked with a zinc ion binding group, such as trapoxin, HC-toxon, Apicidin, FK228 and Largazole; (4) compounds of benzamides, the activity of such compounds of benzamides is lower than that of compounds of hydroximic acids and compounds of cyclopeptides, but the compounds of benzamides have higher selectivity on the HDAC of the I category, such as MS-275, Cl-994 etc. In 2006, American Food and Drug Administration (FDA) approved the suberoylanilide hydroxamic acid (SAHA) of Merck Co., Ltd. to come into the market as vorinostat (Zolinza), the suberoylanilide hydroxamic acid is used for treating CTCL and is the first HDAC inhibitor antitumor drug available in the market.
FK228 (romidepsin) is bicyclic tetrapeptide separated from the broth medium of chrombacterium violaceum. FK228 has a specific bicyclic structure, and a bicyclolactone structure is formed of four amino acid residues (L-Val, L-2-amino-2-butylenoic acid, D-Cys and D-Val) and (3S, 4R-3-hydroxy-7-mercapto-4-heptenoic acid) through a disulfide bond. FK228 has similar selectivity on HDAC1 and HDAC2. The results of the computer simulation show that the thiol group of FK228 may be bonded with Zn2+ through one water molecule. American FDA approved the cyclopeptide FK228 to come into the market as a drug for injection istodax (romidepsinon) on Nov. 6, 2009, it is also used for treating CTCL and becomes the second HDAC inhibitor available in the market following Zolinza, and the researches thereof for treating chronic lymphocytic leukemia, acute myeloid leukemia and other solid tumor are in the clinical stage.
Since the diseases, in particular cancers, related to the dysregulation of HDAC are high in morbidity and poor in prognosis, and the existing pharmaceuticals are dubious in curative effects and has much toxic or side effects, novel high-efficiency and low-toxicity HDAC inhibitors are required, and therefore the invention is designed for this purpose.
Content of the Invention
The invention provides HDAC inhibitors of cyclopeptides, which are used for overcoming the defects that the existing pharmaceuticals are dubious in curative effects and has much toxic or side effects. The invention also provides preparation methods and pharmaceutical applications of the HDAC inhibitors of cyclopeptides.
First of all, the invention provides a cyclopeptide compound with a chemical structure shown as Formula I, and pharmaceutically acceptable salt, isomer, racemate, prodrug or solvate thereof.

Where,
R1 group is hydrogen, C1-12 alkyl, —CH2—O—(C1-12 alkyl), —CH2—NH—(C1-12 alkyl), —CH2—S—(C1-12 alkyl), C6-12 aryl, heteroaryl, —CH2—(C6-12 aryl) or —CH2-heteroaryl; the C6-12 aryl, heteroaryl, —CH2—C6-12 aryl and —CH2-heteroaryl may contain one or more substituents which may be halogen, amino, hydroxyl, nitro, cyano, C1-12 alkyl, C1-12 alkoxy, amino C1-12 alkyl, acyl, acyloxy, thio C1-12 alkyl, carboxyl or phenyl;
R2 and R3 groups are independently selected from hydrogen, C1-12 alkyl, —O—(C1-12 alkyl), —NH—(C1-12 alkyl), —S—(C1-12 alkyl), C6-12 aryl or heteroaryl;
R4 group is hydrogen, C1-12 alkyl, —O—(C1-12 alkyl), —NH—(C1-12 alkyl), —S—(C1-12alkyl), C6-12 aryl or heteroaryl;
R5 group is hydrogen, C1-12 alkyl, C3-12 cycloalkyl, —O—(C1-12 alkyl), —NH—(C1-12 alkyl) or —S—(C1-12 alkyl);
R6, R7 and R8 groups are independently selected from hydrogen, C1-12 alkyl or t-butyloxycarboryl;
 represents a single bond or a double-bond;
X is
where R9 group is hydrogen, C1-12 alkyl, —O—(C1-12 alkyl), —NH—(C1-12 alkyl), —S—(C1-12 alkyl), C6-12 aryl, heteroaryl, halogen, amino, hydroxy, nitro, cyano or carboxyl;
Or, X is a benzene ring which may contain one or more substituents, the substituent may be halogen, amino, hydroxy, nitro, cyano, C1-12 alkyl, C1-12 alkoxy, amino C1-12 alkyl, acyl, acyloxy, thio C1-12 alkyl, carboxyl, phenyl or heterocyclic substituent.
Further, in the above cyclic peptide compound,
R2 is H,
 part is a double-bond,
R4 is hydrogen or C1-12 alkyl.
Further, in the above cyclic peptide compound,
R3 is hydrogen or C1-12 alkyl,
R5 is hydrogen, C1-12 alkyl or C3-12 cycloalkyl,
R6, R7 and R8 groups are independently selected from hydrogen.
Further, in the above cyclic peptide compound,
R3 is methyl,
R6, R7 and R8 groups are all hydrogen,
X is
and
where R9 group is hydrogen.
Further, the compound is selected from:

The invention further provides a method for preparing the cyclic peptide compound as shown in Formula I, comprising the steps as follows:
(1) The condensation of compounds of Formulae II and III with organic alkali under a condensation agent affords the compound of Formula IV. The reaction process is shown as follows:

(2) The condensation of compounds of Formulae IV and V with organic alkali under a condensation agent affords the compound of Formula VI. The reaction process is shown as follows:

(3) The amino protecting group P in the compound of Formula VI is removed, and then the intramolecular cyclization of the compound under a condensation agent and organic alkali affords the compound of Formula I. The reaction process is shown as follows:
Where,                R1, R2, R3, R4, R5, R6, R7 and R8 are the same as those in claim 1;        P is an amino protecting group.        
Further, the condensation agent may be DCC, EDC, HATU, HOAt, HOBt, DEAD, HBTU or PyBOP; the organic alkali is selected from imidazole, triethylamine, diisopropylethylamine, piperidine, lutidine, LiHMDS, NaHMDS, KHMDS, N-methylmorpholine, DABCO or pyridine; and the amino protecting group P is selected from Boc, Cbz, Bn, Fmoc, Alloc, Tos, Tfa, Trt or Bn.
The invention also provides a method for preparing a compound of Formula II, comprising the steps as follows:
(1) L-malic acid is methyl esterified and then reacts with sodium borohydride and acetum to obtain compound a, and then compound a reacts with tert-butyldimethylsilyl chloride and organic alkali (wherein, OCH3 is substituted by trimethylsilyl ester protecting group) to obtain compound b. The reaction process is shown as follows:

(2) Compound b reacts with camphorsulfonic acid to obtain compound c, compound c is then oxidized to obtain aldehyde and compound d, the aldehyde and compound d react with organic alkali to obtain compound e. The reaction process is shown as follows:

(3) Compound e reacts with camphorsulfonic acid to obtain compound f, then compound f, substituted thioacid and triphenylphosphine react with a condensation agent to obtain compound g, and compound g reacts with camphorsulfonic acid to obtain the compound of Formula II.
In the above synthesis process, the indispensable organic solvents may be selected from dichloromethane, tetrahydrofuran (THF), dimethylformamide (DMF), ethylene glycol dimethyl ether, 1,2-dichloroethane, dimethyl phthalate (DMP), methanol, ethanol, petroleum ether, n-hexane or diethyl ether; the indispensable inorganic alkali may be selected from sodium hydroxide, lithium hydroxide, potassium carbonate, sodium carbonate, sodium bicarbonate or calcium carbonate; and the indispensable acid may be selected from trifluoroacetic acid, hydrochloric acid, sulfuric acid or nitric acid. The oxidants may be Dess-Martin oxidants, Swern oxidants, m-chloroperbenzoic acid, pyridinium dichromate (PDC) or pyridinium chlorochromate (PCC).
The invention also provides applications of the above compounds in preparing pharmaceuticals for preventing or treating mammal diseases related to the dysregulation of HDAC.
Further, the mammal diseases related to the dysregulation of HDAC include cancers, neurodegenerative diseases, malaria and diabetes.
Further, the mammal diseases related to the dysregulation of HDAC include lymphoma, lung cancers, gastric cancers, pancreatic cancers, breast cancers, prostate cancers, leukemia, cervical cancers and colon cancers.
It should be noted that, the related terms, such as “alkyl”, “aryl”, “heteroaryl”, “halogen” and “acyl”, used in the text almost have the same general meanings as these terms in the field.
For example, the term “alkyl” refers to straight chain or branched chain. C1-n alkyl represents saturated aliphatic hydrocarbon of 1 to n carbon atoms, including straight chain or branched chain, for example, “C1-12 alkyl” refers that the group is alkyl and there are 1 to 12 carbon atoms on the carbon chain of alkyl. It should be noted that, when there is no special restriction to the number of carbon atoms, the number of carbon atoms only refers to the number of carbon atoms on the specified alkyl part and does not include the number of carbon atoms on the substituent of alkyl.
Those of ordinary skill in the art should know meanings of the following terms or abbreviations.
The term “pharmaceutically acceptable salt” refers to salt that is applicable to be in contact with tissues of mammals, in particular human beings, without excessive toxicity, stimulation or anaphylaxis in a rational medical judgment range, and is proportional to a rational risk-benefit ratio, for instance, amine, carboxylic acid and pharmaceutically acceptable salt of other types of compounds are well-known in the field.
The term “isomer” refers to two or more compounds with same molecular composition and different structures and properties.
The term “racemate” refers to an equimolar mixture of chiral molecules with optical activity and enantiomers of the chiral molecules, the mixture is formed by equivalently mixing molecules with same optical activity capability and opposite optical activity direction, and the racemate is optically inactive as its optical activities counteract with each other due to molecular interactions.
The term “solvate” refers to a mixture of compounds and solvents, for example, crystal is a solvate.
The term “prodrug” refers to compounds for generating parent compounds with the above chemical formulae by hydrolyzing in blood and quickly transforming in vivo.
Substances corresponding to the English abbreviations used in Claims or Specification are respectively:
DCC (N,N′-dicyclohexylcarbodiimide, Cas No.: 538-75-0), EDCl [1-ethyl-(3-dimethylaminopropyl) carbodiimide hydrochloride, Cas No.: 25952-53-8], HATU (Cas No.: 148893-10-1), HOAt (Cas No.: 39968-33-7), HOBt (1-hydroxy-benzo-triazole, Cas No.: 2592-95-2), DEAD (diethyl azodicarboxylate, Cas No.: 1972-28-7), HBTU (Cas No.: 94790-37-1), PyBOP (benzotriazole-1-yl-oxytripyrrolidinophosphonium hexafluorophosphate, Cas No.: 132705-51-2), DIPEA (N,N-diisopropylethylamine, CAS No.: 7087-68-5); LiHMDS [lithium bis(trimethylsilyl)amide], NaHMDS (sodium Hexamethyldisilazide), KHMDS (potassium bis(trimethylsilyl)amide), DABCO (1,4-diazabicyclo[2.2.2]octane). The amino protecting group P is selected from Boc (t-butyloxycarboryl), Cbz (benzyloxycarbonyl), Bn (benzyl), Fmoc (fiuorenylmethoxy carbony), Alloc (propoxycarbonyl), TOS (Tosyl), TFA (trifluoroacetic acid) or Trt (triphenylmethyl).